For performing the testing of semiconductor devices in which it is necessary to provide to and/or accept from the devices analog and digital signals of high frequency, there have been efforts to reduce mutual interference or degradation of these signals during transmission.
For example, Japanese Utility Model Application No. 61-11294 entitled "Probe Apparatus" and Japanese Utility Model Application No. 61-11295 entitled "Probe Apparatus," both filed on Jan. 29, 1986 by Yokogawa-Hewlett-Packard, Ltd., disclose configurations which are intended to preserve a coaxial structure as far ahead as possible when connecting a probe card, equipped with probes being brought into contact with a semiconductor to be measured, electrically with a measuring apparatus. According to these prior applications, a thick metal ring is provided for connecting the probe card with the measuring apparatus. Through openings or holes are formed in the thick wall of the metal ring and extend parallel to the axis thereof. Embedded in these holes are contact probes, each serving as an inner conductor of the coaxial structure. The inner wall of each hole serves as the outer conductor of the coaxial structure.
Such a structure, however, still tends to introduce interference from the digital signal system into the analog signal system, both of which should be of high speed and high accuracy because the digital and analog signal systems are already close to each other at the entrance portion of the ring on the side of the measuring apparatus (including the signal sources). This interference will be described below in greater detail with reference to a drawing.